For certification purposes, some governmental regulatory agencies have mandated that rotorwing aircraft be able to takeoff without extraordinary pilot skills. This has been interpreted to mean that the aircraft should be designed to implement what is known as a fixed collective takeoff (FCTO). A FCTO is a takeoff from a steady hover, at an altitude below the height-velocity diagram for the aircraft, and without any collective variation. This takeoff is typically accomplished by a slight forward cyclic, to establish a forward velocity with minimal altitude loss. At some forward velocity, translational lift occurs permitting takeoff. It is noted that during the time between the cyclic movement and the altitude increase caused by the translational lift, the aircraft may not contact the ground.
In many instances, the maximum load of a rotorwing aircraft is limited by the ability to accomplish a FCTO. Moreover, the ability to successfully complete a FCTO can be exacerbated by the gas turbine engine control for the aircraft. This is because when the translation lift occurs during the FCTO, the rotor load decreases, resulting in an increase in rotor speed. The gas turbine engine control, in response to the increased rotor speed, reduces the fuel flow to the engine, thus reducing the engine speed and horsepower. The decrease in engine horsepower in turn results in a loss of aircraft altitude.
Hence, there is a need for a system and method for a FCTO to be accomplished in a rotorwing aircraft that does not adversely impact the maximum load of the aircraft and/or does not result in an undesirable reduction in engine horsepower during a FCTO. The present invention addresses at least these needs.